Arrangement to holders for cutting bits



June 20, 1967 s. E. l.. JoNssoN A3,325,877

ARRNGEMENT TO HOLDERS FOR CUTTING BITS y rij \ INVENTOR n i QW w ATTORNEYS United States Patent O 3,325,877 ARRANGEMENT TO HOLDERS FOR CUTTING BITS Stig Evert Lennart `lonsson, Lidingo, Sweden, asslgnor to Stora Kopparbergs Bergslags Aktiebolag, Falun, Sweden, a joint-stock company limited Filed Nov. 26, 1965, Ser. No. 509,948 Claims priority, application Sweden, Dec. 9, 1964, 14,858/ 64 4 Claims. (Cl. 29-96) The present invention -relates to an arrangement in such cutting bit holders provided with a clamping jaw for lixing cutting bits, a so called reversible bit made of hard metal for example, and possibly chip breakers in a seating in the holder, which clamping jaw can be tightened by means of a fixer-bolt, said clamping jaw being provided with a backwardly directed overhang provided with a stop member cooperating with a corresponding latch member arranged stationary in the body `of the holder so as to prevent rotation of the clamping jaw around the axis of the bolt.

Bit holders of the type described above are previously known in which the overhang, projecting backwards from Athe clamping jaw, is used either for iixing the jaw in relation to the body -of the bit holder or for balancing the jaw so that it will lie tight against the bit without becoming obliquely adjusted in relation to the lixer bolt.

Even though bit holders and clamping jaw arrangements of this type are very elfective in many respects, =it is often shown that the bit becomes displaced out of the required close contact `with the support surfaces of the seating at that moment of being gripped by the clamping jaws. When precision arrangements are involved, even the slightest displacement could mean great inconvenience and necessitate re-positioning of the complete bit holder, which one lwill preferably completely avoid by using so called reversible bits, which when once in a correct position lin the seating always keep a uniform position when being replaced.

A further problem is that when it is necessary to attain a high degree of accuracy, the guide arrangements in arrangements known at present for fixing the clamping jaw, must be manufactured to such close tolerances that assembly of the various sections in the bit holder is made more diicult, and at the same time manufacture of the same becomes more expensive.

The object of the invention is to Iprovide-in bit holders of the type mentioned in the preamble-an arrangement which in a simple way automatically effects a suitable backward fraction of the bit `and chip-breaker respectively against the support surface of the seating in the body of the bit holder, whilst at the same time carrying out an exact setting of the clamping jaw in relation to the body of the holder.

In accordance therewith the invention is characterized in that the overhang is provided with a stop member cooperating with a corresponding stationary latching member in the body of the holder so as to prevent rotation of the clamping jaw around the axis of the bolt, said stop member Vand latching member being moreover provided with mutually cooperating contact surfaces arranged in such direction that the clamping jaw at the moment of clamping is forced backwards in such a degree and direction that the work-piece or pieces to be clamped are brought into close contact with the support surfaces of the seating.

The invention will now be more closely described with reference to an embodiment of the same shown diagrammatically on the attached drawing, and in conjunction therewith further characterizing features of the invention will be disclosed.

FIGURE l shows in perspective the foremost end of a bit holder with a reversible bit mounted in a seating herein, and also a chip breaker situated on top of said bit and secured by means of a clamping jaw according to the invention.

FIGURE 2 shows a vertical section through the bit holder and the clamping jaw in engaged position.

FIGURE 3 is a horizontal section taken along the line III-III in FIGURE 2.

The reference numeral 1 in the drawing indicates the body of a bit holder provided at its foremost corner, with a substantially triangular seating 2 having support surfaces and side surfaces arranged at angles suitable for working purposes. A triangular bit 3 is positioned in the mounting 2, which bit has a projecting cutting corner 4. A chip breaker 5 has also -been positioned in said mounting on top of the bit 3.

A fixer bolt 7 is also arranged in the body of the bit holder and is capable of being screwed in or out by means of threads 6. The upper end of said xer bolt is provided with threads 8, suitably of lower pitch than threads 6. A clamping jaw 9 is screwed onto the threads 8 on the upper section of the bolt, which jaw has a forward clamping member 10 lying in abutment-under considerable pressurewith the chip breaker 5 and holds said chip breaker 5 as well as the bit 3 in a xed position in the seating 2. As can be seen from the gure, the upper end of the iixer bolt is provided with a hole 11 intended for receiving a suitable Spanner when said bolt is to be rotated for the purpose of tightening or untightening the clamping jaw 9 into or out of its engaging position, and a lower Spanner hole 12 which enables the fixer bolt to be also moved from undernearth with the assistance of a suitable Spanner.

The clamping jaw 9 is further provided with an overhang 13 provided with a boss 14 and which is directed backwards in relation to the clamping member 10.

For closer explannation of the method and construction of the clamping jaw according to -FIGURE 1 reference is made -to FIGURES 2 and 3, wherein the same reference numerals allotted those members in FIGURE 1 are also in FIGURES I2 and 3, whereby, however, the chip breaker is omitted in FIGURE 2.

As can be `seen from FIGURE 2 the boss 14 extends downwards into a hole 15 in the body of the holder. This hole presents a conical bottom with sloping Contact surfaces 16, against which the boss, which in the example is assumed to have been rounded olf in the form of a sphere, is intended to lie and slide downwards forcing the entire clamping jaw 9 backwards in its moment of engagement.

The boss 14 is, however, also intended for another purpose, namely to prevent the clamping jaw 9 from rotating around t-he axis of the yi'ixed bolt, and to achieve this purpose the hole 15 is so adapted that lthe boss `14 is -given no possibility to rotate in a direction essentially at right angles to the plane represented in FIGURE 2. However, the hole can be so 4dimensi-oned that the boss is able to rota-te, to a limited degree, to the right in FIGURE 2.

In order to make it possible in contradistinction to that which has previously been aimed at in such clamping jaws, to move the clamping jaw 9-despite it being relatively firmly -screwed into the xer bolt 7-backwards in the `direction of the arrow A so that lthe bit 3 is pressed in a determined direction for example-against the side surface 17 of the seating into close abutment thereagain-st, said clamping jaw 9 has been provided with a downwardly projecting internally threaded sleeve 18, extending down into a recess 19 in the body of the bit holder 1. The outer periphery of this sleeve is, however, in accordance wit-h FIGURE 3, made oval so that two slightly crescent shaped clearances 20 and 21 are formed on the left and right side of the centre 22 between the sleeve and the 4wall of the recess 19, which wall is completely circular. As is evi- `dent from FIGURE 3 the sleeve in zones 23 and 24 is situated close to the Wall of the recess 19 whereas a limited possibility of the sleeve 18 being in an oblique position is found in a plane represented by the line 25. Due to a certain clearance in the threads and this possibility of the sleeve 18 positioning obliquely, although very slight, it is possible on tightening the clamping jaw 9 (see FIGURE 2)-after the clamping member 10 has been engaged with the bit 3 by further rotation of the fixer bolt 7-to cause the boss 14 to slide down t-he surface 16 to a limited degree and thereby to draw the complete clamping jaw 9 in the direction of the arrow A sufficiently so as to achieve close contact between the bit 3 and the surface 17. Due to this possibility of backward movement one can always be certain that the bit automatically fits exactly in its seating 2 in the -bit holder. Moreover the zones 23 and 24 of the sleeve, on this backward movement of the clamping jaw, are brought in guiding contact with the corresponding wall lsections of the hole 19 so that the clamping jaw is locked in a very exact position in relation to the body of the holder.

Although a boss 14 is described in the example as being arranged on the clamping jaw proper and a corresponding hole 15 in the holder body, the condition can be the direct opposite i.e. the Ihole can be located in the clamping jaw and the boss projecting from the body of the bi`t holder. Further it is not necessary for the `boss 14 to be spherical in shape, the most important fact being that cooperating surfaces on both the members which serve in producing said extra displacement movement backwards, can be |arranged in a suitable manner for this purpose.

The invention is not restricted to the shown and described embodiment lof the same but can be varied in an arbitrary manner within t-he yscope of the following claims.

What is claimed is:

1. In a cutting bit holder provided with a clamping jaw for fixing cutting bits disposed in a seating in the body of the holder, which clamping jaw is tightened by means of `a differentially threaded fixer bolt threadably engaging said body and jaws, the improvement comprising a backwardly directed overhang provided on said jaw and having Ia `stop member cooperating with a corresponding latch member arranged stationary in the body of the holder so as to prevent rotation of the clamping jaw around the axis of the bolt, and mutually cooperating contact surfaces arranged on said stop member and latch member, said surfaces bein-g shaped so that the clamping jaw, at the moment of clamping, is forced backwards to such a degree and direction that the bit to be clamped is brought into close contact with all the support surfaces of the seating.

2. The improvement according to claim 1, wherein the stop member is formed by a bos-s on the under surface of the overhang and the latching member is formed by a recess formed in the body of the holder and having a surface which is inclined in such a way that the boss, on said clamping action, is forced downwardly with respect to said surface in a direction which causes said backward movement of the clamping jaw.

3. An arrangement according to claim 1, further comprising a sleeve disposed on the clamping jaw and a circular hole formed in the body of the holder and adapted to receive said sleeve to guide said jaw with respect to said body, t-he outer circumference lof said sleeve being slightly oval so that crescent shaped clearances are formed between the `sleeve and the wall of t-he hole, said clearances lying in a plane passing through said direction of movement and extending to either side of lsaid sleeve, the Temaining portion of the sleeve closely fitting the wall of said hole.

4. The improvement according to claim 1, further cornprising a chip breaker disposed between said bit and said clamping jaw.

References Cited UNITED STATES PATENTS 1,396,180 11/19221 Fors 29-96 1,776,335 9/1930 Ravzieres 29-96 2,181,023 1'1/1939 Moore 29-96 3,002,405 10/ 1961 Heftle'r 29-96 3,156,031 ll/1964 Lundgren 29-96 HARRISON L. HINSON, Primary Examiner. 

1. IN A CUTTING BIT HOLDER PROVIDED WITH A CLAMPING JAW FOR FIXING CUTTING BITS DISPOSED IN A SEATING IN THE BODY OF THE HOLDER, WHICH CLAMPING JAW IS TIGHTENED BY MEANS OF A DIFFERENTIALLY THREADED FIXER BOLT THREADABLY ENGAGING SAID BODY AND JAWS, THE IMPROVEMENT COMPRISING A BACKWARDLY DIRECTED OVERHANG PROVIDED ON SAID JAW AND HAVING A STOP MEMBER COOPERATING WITH A CORRESPONDING LATCH MEMBER ARRANGED STATIONARY IN THE BODY OF THE HOLDER SO AS TO PREVENT ROTATION OF THE CLAMPING JAW AROUND THE AXIS OF THE BOLT, AND MUTUALLY COOPERATING 